There has been an ever increasing demand in security, warfare, and peacekeeping applications for a manner to accurately detect the presence of dangerous materials, such as concealed weapons, chemicals, or explosives. In the case of concealed explosives or chemicals, it is typically necessary to detect the materials from a suitable standoff distance, so as to avoid danger to the individuals that attempt to detect the concealed materials. Furthermore, it may be desirable to identify the specific type of materials, such as to determine a source of the dangerous materials or to assess the potential for damage or harm resulting from detonation or release of the dangerous materials.
There are many techniques that have been efficiently used in detecting whether certain dielectric materials, such as chemicals or explosives, are present and/or in identifying the type of dielectric material. For example, typical detection/identification systems include cavity resonators, spectroscopes, time domain reflectors, and a variety of other techniques. However, most such techniques are either laboratory based techniques or contact techniques. As a result, the techniques are unable to be used in the context of a field operation or at a large public event (LPE) where farther standoff distances are required. In addition, certain detection techniques are unable to penetrate intervening materials, such as clothing and/or precipitation or atmospheric conditions.